Method for packaging, thermoforming machine and package

ABSTRACT

The disclosure relates to a method for manufacturing a package whereby a packaging tray is formed into a packaging film and filled with a product. The disclosure is distinguished by the fact that at least the inner and/or outer side of the packaging tray is covered with a barrier layer after the forming of the packaging tray. The disclosure also relates to a thermoforming machine for carrying out this method as well as to a package manufactured by means of the method.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims foreign priority benefits under 35 U.S.C.§119(a)-(d) to European patent application number EP 10 008 471.4 filedAug. 13, 2010, which is incorporated by reference in its entirety.

TECHNICAL FIELD

The disclosure relates to a method for manufacturing a package, athermoforming machine for forming a package and to a package that can bemanufactured by means of the method or with the thermoforming machine.

BACKGROUND

The manufacturing of packages by using thermoforming machines iswidespread. Such a thermoforming machine in which packaging trays arethermoformed with a packaging film that is usually made of plastic andfilled with a product is described in DE 10 2007 013 698 A1.

DE 10 2007 013 698 A1 already discloses that the characteristics of thepackage, particularly the gas permeability of the packaging material,can have a substantial influence on the shelf-life of the perishablegoods contained in the package. These goods can be, in particular,foodstuffs.

EP 0 872 164 B1 and WO 2008/046553 A1 disclose devices for generatingmicrowave plasmas. These two documents suggest that workpieces can becovered by means of a plasma treatment in which they are exposed to themicrowave plasma generated by the devices. The two documents do not,however, contain any reference whatsoever to packages or packagingmethods.

SUMMARY

An object of the present disclosure is to improve a method formanufacturing a package, a thermoforming machine and a package itself tothe effect that a longer shelf-life is achieved for the packagedproducts by means of the simplest possible design means.

A method according to the present disclosure is distinguished by thefact that at least the inner and/or the outer side of the packaging trayis covered with a barrier layer after the forming of the packaging tray.This gas barrier layer influences the gas permeability of the packagingfilm, in particular the permeability for oxygen. By reducing thetransfer of oxygen through the packaging film, the barrier layer extendsthe shelf-life of a packaged product. The application of the barrierlayer onto the packaging tray after the forming of the packaging trayhas, in comparison to the also theoretically possible use of a packagingfilm already covered before the forming of the packaging tray, theadvantage that excessive stretching and loading of the barrier layer areavoided during the forming of the packaging tray. This makes it possiblealso to use very thin barrier layers.

In a variant of the present disclosure, the covering with the gasbarrier layer takes place even before the filling of the packaging traywith a product. In this way, the covering can be carried out without thepossibly disturbing presence of the product.

Additionally or alternatively, the covering of the outer side of thepackage, i.e., the packaging tray and/or a top film that seals thepackaging tray, can take place after the manufacture of the entirepackage, i.e., after the packaging tray has been sealed with the topfilm. The advantage of this variant is that in this way, even very thinor flexible films can be covered, in particular, skin films. After theapplication of the skin film used as the top film to the product under avacuum, the skin film can no longer move. This prevents the gas barrierlayer, which is only applied later, from peeling off.

The barrier layer preferably has an oxygen permeability level of lessthan 10 cubic centimetres (ccm) per (m²×24 hours×pressure difference[bar]). In other words, in this case an oxygen volume of less than 10ccm occurs or passes through each square metre (m²) of the packagingfilm provided with the barrier layer per 1 bar pressure differencebetween two opposite sides of the packaging film and barrier layer in 24hours. This very low oxygen permeability rate guarantees a very longshelf-life for the product in the packaging.

It has proven to be particularly advantageous if the covering of thepackaging tray with the barrier layer takes place by means of a plasmacovering. This type of packaging makes it possible to apply extremelygas-impermeable barrier layers with a continuously constant thicknesseven on to packages with complicated shapes.

The plasma needed for the plasma covering can, for example, be createdin a packaging machine used for manufacturing the package. In this way,the plasma covering device is integrated into the packaging machine, andthe entire packaging machine is much more compact than if an additionalplasma covering system were to be provided.

The method according to the present disclosure is particularly suitablefor the use of a biodegradable packaging film. Very low gas-transferrates can also be achieved here with conventional multi-layer films, forexample, with an EVOH film (ethylene vinyl alcohol film). These have thedisadvantage, however, that they have to be comparatively thick and thatthe gas barrier layer is very sensitive to moisture with the EVOH film.This barrier layer could consequently become more gas-permeable againif, for example, moist foods are contained in the package. This, inturn, reduces the shelf-life.

Biodegradable films, for example, films made of bioplastics such as PLA(polylactide, polylactic acid) are normally very gas-permeable. Themethod according to the disclosure now makes it possible to apply a verythin barrier layer to these films in order to reduce their gaspermeability without the disadvantage of significantly impairing thebiodegradability of these films.

The barrier layer itself may comprise or consist of, for example,silicon oxide (SiOx) and/or aluminium oxide (AlOx).

The present disclosure also relates to a thermoforming machine with aforming station for forming packaging trays into a packaging film, aswell as with a filling station. The disclosure provides for a coveringstation to be provided between the forming station and the fillingstation and/or downstream of a station for sealing the packaging trayswith a top film, whereby this covering station is developed such that atleast the inner and/or the outer side of the packaging tray is coveredwith a barrier layer. The advantages described above are achieved inthis way.

The covering station can, for example, be set up for applying a barriercovering with a thickness of less than a micrometre. Even with such avery thin layer, the gas permeability of the packaging material can begreatly limited.

The present disclosure furthermore relates to a package with a packagingtray formed from a packaging film that can be thermoformed in which theinner and/or outer side of the packaging tray is covered with a barrierlayer.

It has already been explained that the packaging film is preferablybiodegradable.

In order to guarantee a particularly long shelf-life, it is advantageousif the packaging film provided with the barrier layer has an oxygenpermeability level of less than 10 ccm per (m²×24 hours×pressuredifference [bar]).

In an advantageous variant of the disclosure, the barrier layer is notsensitive to moisture. As a result, it is particularly suitable for usein a package that is packed with moist foods.

The barrier layer may comprise SiOx and/or AlOx.

In the following, an advantageous embodiment of the present disclosureis described in more detail with reference to the below drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic view of a thermoforming machine according to thepresent disclosure; and

FIG. 2 is a schematic cross-sectional view of a package according to thepresent disclosure.

DETAILED DESCRIPTION

FIG. 1 shows, in a schematic side view, a packaging machine 1 accordingto the present disclosure in the form of a thermoforming machine. Thepackaging machine 1 has a forming station 2. Packaging trays 5 areformed in the forming station 2 into a packaging film 4 drawn from afilm roll 3 by means of thermoforming.

A product 7 is introduced into the packaging trays 5 at a fillingstation or loading station 6. This product 7 can be a food, preferably afood 7 with a certain moisture level.

A sealing station 8 of the packaging machine 1 is used to seal thepackaging trays 5 with a top film 9. The top film 9, which can, like thepackaging film 4, be a sealable plastic film, is drawn from a furtherfilm roll 10. The top film 9 arrives in the sealing station 8 via a rollguide 11.

A hermetically sealed sealing chamber can be formed around the packagingtray 5 in the sealing station 8. This sealing chamber is evacuated andpossibly gassed with a replacement gas before a sealing tool seals thetop film 9 to the packaging tray 5, preferably at the edges of thepackaging tray 5. The part of the top film 9 that juts out beyond thepackaging tray 5 can be separated from the now sealed package 13 whilethe packaging tray 5 is still in the sealing station 8. The remainingfilm grid 14 of the top film 9 is fed to a remaining film winder 15 andcollected there.

Downstream of the sealing station 8 in the direction of production P, across-wise cutting device 16 and a longitudinal cutting device 17 ensurea separation of the packages 13 that until now have been in aninterconnection of the packaging film 4. A conveyor belt 18 is used totransport the finished and separated packages 13.

A covering station 19 is provided, between the forming station 2 and thefilling station 6 in the direction of production P. In the embodimentshown, the covering station 19 is a plasma covering station 19. Thecovering station 19, which is integrated into the packaging machine 1,has a plasma generation device 20, known, for example, from WO2008/046553 A1, which is likewise depicted only schematically in FIG. 1.The plasma generated by means of the plasma generation device 20 is usedin order to cover with a thin barrier layer the inner and/or outer sideof the packaging trays 5 in the covering station 19 by means of a plasmacovering or by means of plasma-enhanced chemical vapour deposition(PECVD).

In an embodiment of the method according to the present disclosure or inthe event of operation of the packaging machine 1 shown in FIG. 1, thispackaging machine is operated in cycles. A section of the packaging film4 is drawn off of the film roll 3 with each work cycle. When thepackaging film 4 comes to a standstill, the forming station 2 closes inorder to thermoform a packaging tray 5 or a field of packaging trays 5lying next to one another into the packaging film 4.

When the transport continues, the packaging trays 5 arrive in thecovering station 9, in which their inner and/or outer side is given athin gas barrier layer.

After the packaging trays 5 have been filled with a product 7 in thefilling station 6, they arrive in the sealing station 8. There a vacuumis created in the packaging trays 5 and/or a replacement gas (mixture)is fed into the packaging trays 5 before the packaging trays 5 aresealed with the top film 9 in a gas-tight seal. As the now sealedpackages 13 are further transported in the direction of production P,the packages 13 are separated by means of the cross-wise andlongitudinal cutting devices 16, 17.

FIG. 2 shows a schematic vertical cut through an embodiment of a package13 according to the present disclosure, whereby it is possible tomanufacture the package 13 with the packaging machine 1. The package 13has a packaging tray 5 that is shaped by means of thermoforming into thepackaging film 4. The packaging film 4 in the depicted embodiment is apackaging film made of a biodegradable plastic, also called bioplastic.For example, this could be PLA (polylactide, polylactic acid).

The packaging tray 5 has an inner side 21 and an outer side 22. In thedepicted embodiment, only the inner side 21 is provided with a gasbarrier layer 23 in the plasma covering station 19. The gas barrierlayer 23 has a thickness of less than a micrometre. It is not sensitiveto moisture, i.e., it does not change its characteristics under theinfluence of moisture. The barrier layer 23 can be made of SiOx or ofAlOx. The area of the packaging film 4 provided with the barrier layer23 has a gas permeability level particularly for oxygen of less than 10ccm per (m²×24 hours×pressure difference [bar]). This guarantees thatonly a negligibly small amount of oxygen can enter into the package 13,so that the product 7 contained in the package 13 is given a longshelf-life.

A top film 9 is sealed on to the edges 24 of the packaging tray 5,whereby this top film 9 likewise ensures a gas-tight seal of the package13.

Departing from the depicted embodiment, the packaging machine 1according to the disclosure, the method according to the disclosureand/or the package 13 according to the disclosure can be changed in manyrespects. In particular, it is conceivable not to apply the barrierlayer 23 to the inner side 21 or not only to the inner side 21 of thepackaging tray 5, and instead additionally or alternatively to apply itto the outer side 23 of the packaging tray 5. By applying the barrierlayer 23 to both sides 21, 22 of the packaging tray 5, it is possible toprovide a particularly gas-tight package 13.

It was already mentioned that in addition to or as an alternative to thecovering station shown in FIG. 1, a covering station 19 can also bearranged downstream of the sealing station 8, i.e. consequently inbetween the sealing station 8 and the separating device 16. This variantis particularly useful in the event that a very thin film is used as thetop film 9, for example, a skin film that does not have a sufficientlyhigh level of form stability until after it has been applied to thepackaging tray 5. In a covering station 19 downstream of the sealingstation 8, the entire outer side of the package 13 can be given a gasbarrier layer 23, i.e., the outer side 22 of the packaging tray 5 andthe outer side of the top film 9.

In a further variant, it is conceivable that the outer and/or the innerside of the top film 9, i.e., the side of the top film 9 facing awayfrom or towards the packaging tray 5, is covered with a gas barrierlayer 23. For this purpose, a (further) covering station 19 can beprovided in the area of the feed of the top film 9 to the sealingstation 8.

It is furthermore conceivable to provide an aluminium layer as a gasbarrier layer 23 that is applied to the packaging tray 5 and/or the topfilm 9 by means of vaporization. Disadvantageous in the case of analuminium covering, however, is that the areas of the package 13 coveredwith it are no longer transparent under some conditions. A covering, forexample, with aluminium oxide and/or silicone oxide has the advantage,in contrast, that only a maximum of 20 percent loss of transparencyoccurs, so that the areas of the package 13 provided with the barrierlayer 23 still continue to remain transparent.

While various embodiments have been illustrated and described above, itis not intended that these embodiments illustrate and describe allpossible forms of the invention. Rather, the words used in thespecification are words of description rather than limitation, and it isunderstood that various changes may be made without departing from thespirit and scope of the invention.

What is claimed is:
 1. A method for manufacturing a package, the methodcomprising: forming a packaging tray in a packaging film; covering atleast an inner side and/or an outer side of the packaging tray with abarrier layer after the forming of the packaging tray; introducing aproduct into the packaging tray; and sealing the packaging tray with atop film after the introducing step.
 2. The method according to claim 1wherein the covering step is performed before the introducing step. 3.The method according to claim 1 wherein the covering step is performedsuch that that the outer side of the packaging tray and/or an outer sideof the top film is/are covered with the barrier layer after the sealingof the packaging tray with the top film.
 4. The method according toclaim 1 wherein the barrier layer has an oxygen permeability level ofless than 10 ccm per (square metre×24 hours×pressure difference [bar]).5. The method according to claim 1 wherein the barrier layer comprisesplasma.
 6. The method according to claim 5 wherein the plasma isgenerated in a packaging machine used for manufacturing the package. 7.The method according to claim 1 wherein the packaging film isbiodegradable.
 8. The method according to claim 1 wherein the barrierlayer comprises silicon oxide and/or aluminum oxide.
 9. A thermoformingmachine comprising: a forming station for forming packaging trays into apackaging film; a filling station for introducing products into thepackaging trays; and a covering station provided downstream of theforming station for covering at least an inner side and/or an outer sideof the packaging tray with a gas barrier layer.
 10. The thermoformingmachine according to claim 9 wherein the covering station is arrangedbetween the forming station and the filling station.
 11. Thethermoforming machine according to claim 9 further comprising a sealingstation for sealing the packaging trays with a top film, wherein thecovering station is arranged downstream of the sealing station and isadapted to cover the outer side of the packaging tray and/or an outerside of the top film with the barrier layer.
 12. The thermoformingmachine according to claim 9 wherein the covering station is a plasmacovering station.
 13. The thermoforming machine according to claim 9wherein the covering station is set up for applying the barrier layerwith an oxygen permeability level of less than 10 ccm per (squaremetre×24 hours×pressure difference [bar]).
 14. The thermoforming machineaccording to claim 9 wherein the covering station is set up for applyingthe barrier layer with a thickness of less than 1 μm.
 15. A packagecomprising: a packaging tray thermoformed from a packaging film; a topfilm sealed to the packaging tray; and a gas barrier layer covering aninner side and/or an outer side of the packaging tray and/or the topfilm.
 16. The package according to claim 15 wherein the packaging filmis biodegradable.
 17. The package according to claim 15 wherein thebarrier layer is provided on the inner side and/or the outer side of thepackaging tray, and wherein the packaging tray with the barrier layerhas an oxygen permeability level of less than 10 ccm per (squaremetre×24 hours×pressure difference [bar]).
 18. The package according toclaim 15 wherein the barrier layer comprises silicon oxide and/oraluminum oxide.